1134 Appendix VL
and delivered heat are exactly equal. But if the direct drop be
large, and the reversed rise of temperature small, we shall have
increased the entropy base, and an overplus of heat will have been
obtained from the cold body. This is distinctly shewn by Fig.
1003, where the work areas C and E are naturally equal, while
only the heat H is rejected to the cold body, the larger heat G is
absorbed on reversal, and though the heat D was first supplied
by the coal, the larger quantity F is returned at a lower temper-
ature TB viz., through a decreased rise of temperature r3-r2. It
must be understood that the direct and reversed operations are
here performed in different machines.
Pp. 614 and 884. Initial Condensation and Leakage.
The first report of the Steam Engine Research Committee of .the
Institution of Mechanical Engineers, was made by Professor
Capper, in March 1905, and detailed at considerable length the
trials made upon a horizontal engine, both with and without
jackets, condensing and non-condensing. The leakage of the slide-
valves was measured by blocking the steam ports, and allowing
the lost steam to escape by the exhaust. Leakage was decreased
| by lubrication. The leakage of the piston was measured by
** blocking one steam *port and running the engine single-acting
with the other.
The general conclusions for the particular engine under
experiment were (i) that leakage was nearly independent of
sliding speed and proportional to pressure difference, inversely
| I proportional to lap, and amounted in quantity to over 20% of the
I steam supply: (2) that the initial condensation, taken separately
^ from leakage, diminishes with increase of initial temperature : (3)
that the total missing quantity increases with temperature increase :
(4) that re-evaporation is o*ften greater without than with jackets.
Lastly by plotting heat units for I.H.P., to a base of initial pressure
in both the jacketed and non-jacketed trials, the exact point was
found for temperature and speed when the jackets could be dis-
P. 616. The Steam Engine Indicator.—The usual
forms of indicator are unsuited to engines of extremely high speed
such as are now adopted on motor-cars. The objection of the